For the discharge of ash, slag as well as optionally carbon particles (gasification residues), which accumulate in the pressurized gasification of liquid or solid fuels, various removal systems working intermittently on a dry or wet basis are known.
Thus, a removal device for a fluidized-bed reactor preferably operating under pressure has been proposed, which makes possible a metered material discharge by an adjustable drive and whereby the material to be discharged forms the closing element so that no closing bodies such as slides or the like are provided and whereby the conveyor element is designed as a worm conveyor (cf. DE-OS No. 32 41 239).
A similar principle is put into effect in the case of a pressureless gasification reactor with wet ash removal, in which the particles of the gasification residue are collected in the water-filled axial bottom connection of the gasification reactor and in which a worm conveyor provides for removal of the residue particles that have settled beneath the water surface (EP-OS 0 117 765).
In known systems, especially for dry removal of ash as well as slag constituents, which accumulate during pressurized gasification, locks have been used so far, as is generally done if streams of solids are to be conveyed between spaces of different pressure and the escape of possibly harmful gases has to be prevented. Other apparatus, machines and control devices belong to such removal systems. In this case, one or more bunkers are used which as a rule are placed under the gasification reactor and are separated from one another and from the reactor by combinations of fittings.
An ash discharge with two bunkers is so made, for example, that dry or wet ash from the reactor is conveyed under pressure into the first bunker. After the reactor and bunker are separated, the bunker is expanded, the expansion gases are removed. Then the connection to the second bunker is opened, so that the dry ash or residue water suspension gets into the pressureless container below. In the case of dry ash removal it is additionally necessary to pass scavenging gas through the pressureless container to remove the raw gas containing CO and H.sub.2 S from the ash or residue bed before discharge. Then the connection between the bunkers is closed, and the bunker placed directly under the reactor is covered with nitrogen, carbon dioxide or product gas. The ash or residue is removed from the pressureless bunker by suitable conveyor devices. Such a removal system works intermittently. In covering the bunker with product, gas pressure fluctuations are caused in the gasification system. The control of the ash or residue discharge is expensive since a multiplicity of closing fittings must be used. Especially in the case of dry ash removal the operation of the closing fittings is very maintenance intensive and subject to malfunctions because of wear and tear, formation of grooves and corrosion of the sealing surfaces.